(1) Field of the Invention
The present invention relates to a cantilever for use in supporting a stylus tip of a phonograph pickup, and also to a phonograph pickup cartridge including this cantilever.
(2) Description of the Prior Art
Reproduction characteristics of a pickup cartridge depend mainly on the vibration system thereof, especially the physical properties of a cantilever or stylus arm. Accordingly, various improvements have heretofore been made in connection with the cantilevers. In order to attain uniform reproduction characteristics over all the reproduction frequency range, it is necessary to use a material having a high Young's modulus and a low specific gravity for formation of a cantilever. However, in reproduction of stereo-phonographic records, a cantilever inevitably undergoes torsional moment or bending moment. Thus, even if a material having a high Young's modulus is employed, the cantilever should also have a certain thickness. Accordingly, when a cantilever undergoes such moment during reproduction, a pickup cartridge is kept in such position, i.e., as if it were inclined toward a record, and as a result, distortion of sounds is increased and undesirable frequency characteristics inherent of reproduced sounds become prominent. This is a fatal defect to a pickup cartridge in which very true reproductin is required.
In conventional cantilevers, various improvements have been made so as to eliminate the foregoing defect. For example, materials composed of light metals such as aluminum subjected to various treatments, for example, the anodic oxidation surface treatment, and composite materials including carbon fibers, have been proposed. In these cantilevers, the apparent rigidity is considerably improved, but since a difficult technique is necessary for such special treatment, the productivity is low and the manufacturing cost is high. In case of composite materials, problems are involved in the properties of the respective materials to be combined, and thus troubles are created when these materials are combined to form composite materials. Accordingly, even when these materials are used for formation of cantilevers of pickup cartridges, no substantial effects can be attained.